diff --git a/Python/dynload_aix.c b/Python/dynload_aix.c
index 6a229882f53..013e8f8bf5d 100644
--- a/Python/dynload_aix.c
+++ b/Python/dynload_aix.c
@@ -28,7 +28,7 @@ redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 #endif
 
 
-extern char *Py_GetProgramName();
+extern char *Py_GetProgramName(void);
 
 typedef struct Module {
 	struct Module *next;
diff --git a/Python/dynload_dl.c b/Python/dynload_dl.c
index af95254f334..84fc9c4ed98 100644
--- a/Python/dynload_dl.c
+++ b/Python/dynload_dl.c
@@ -16,7 +16,7 @@ redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 #include "importdl.h"
 
 
-extern char *Py_GetProgramName();
+extern char *Py_GetProgramName(void);
 
 const struct filedescr _PyImport_DynLoadFiletab[] = {
 	{".o", "rb", C_EXTENSION},
diff --git a/Python/frozenmain.c b/Python/frozenmain.c
index f846c2d2c03..576baacc6b9 100644
--- a/Python/frozenmain.c
+++ b/Python/frozenmain.c
@@ -13,9 +13,9 @@ redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 #include "Python.h"
 
 #ifdef MS_WIN32
-extern void PyWinFreeze_ExeInit();
-extern void PyWinFreeze_ExeTerm();
-extern int PyInitFrozenExtensions();
+extern void PyWinFreeze_ExeInit(void);
+extern void PyWinFreeze_ExeTerm(void);
+extern int PyInitFrozenExtensions(void);
 #endif
 
 #ifdef HAVE_UNISTD_H
diff --git a/Python/import.c b/Python/import.c
index 959474a4298..46c84697396 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -817,7 +817,8 @@ is_builtin(char *name)
    pathname and an open file.  Return NULL if the module is not found. */
 
 #ifdef MS_COREDLL
-extern FILE *PyWin_FindRegisteredModule();
+extern FILE *PyWin_FindRegisteredModule(const char *, struct filedescr **,
+					char *, int);
 #endif
 
 #ifdef CHECK_IMPORT_CASE
diff --git a/Python/thread_lwp.h b/Python/thread_lwp.h
index 671387c46cc..8858e911bd2 100644
--- a/Python/thread_lwp.h
+++ b/Python/thread_lwp.h
@@ -106,7 +106,7 @@ void PyThread__exit_prog(int status)
 PyThread_type_lock PyThread_allocate_lock(void)
 {
 	struct lock *lock;
-	extern char *malloc();
+	extern char *malloc(size_t);
 
 	dprintf(("PyThread_allocate_lock called\n"));
 	if (!initialized)